godan verb (-su), transitive verb
confine to a room
Archaic transitive verb meaning to shut someone away in a room or keep them confined indoors. Not used in modern Japanese; the modern equivalent is 閉じ込める or 監禁する.
古い文書には「罪人を幽す」と記されている。
Old documents record 'to confine a criminal to a room'.
The kanji 幽 carries meanings of seclusion and confinement. The exact historical derivation of the verb 幽す is uncertain, but it is an archaic formation no longer productive.